QUADRATICS 1

What must be added to x²  + 20x to make the expression a perfect square?

Solution

a=1, b=20,c=?

b² = 4ac

(20)² = 4 x 1 x c

400 = 4c

400 = 4c

4       4

100 = c

Hence number to be added is 100

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What must be added to x²  + 10x to make the expression a perfect square?